Billiard ball rack



FIG. 1 is a front view of a billiard ball rack showing my new design (the rear view being substantially identical thereto);

FIG. 2 is a top view thereof;

FIG. 3 is a side view thereof (the other side being substantially identical thereto; and

FIG. 4 is a bottom view thereof. 

The ornamental design for a billiard ball rack, as shown and described. 